Hierarchical Formation of Fibrillar and Lamellar Self-Assemblies from Guanosine-Based Motifs

Here we investigate the supramolecular polymerizations of two lipophilic guanosine derivatives in chloroform by light scattering technique and TEM experiments. The obtained data reveal the presence of several levels of organization due to the hierarchical self-assembly of the guanosine units in ribbons that in turn aggregate in fibrillar or lamellar soft structures. The elucidation of these structures furnishes an explanation to the physical behaviour of guanosine units which display organogelator properties

Self-assembly of supramolecular triarylamine nanowires in mesoporous silica and biocompatible electrodes thereof

Biocompatible silica-based mesoporous materials, which present high surface areas combined with uniform distribution of nanopores, can be organized in functional nanopatterns for a number of applications. However, silica is by essence an electrically insulating material which precludes applications for electro-chemical devices. The formation of hybrid electroactive silica nanostructures is thus expected to be of great interest for the design of biocompatible conducting materials such as bioelectrodes. Here we show that we can grow supramolecular stacks of triarylamine molecules in the confined space of oriented mesopores of a silica nanolayer covering a gold electrode. This addressable bottom-up construction is triggered from solution simply by light irradiation. The resulting self-assembled nanowires act as highly conducting electronic pathways crossing the silica layer. They allow very efficient charge transfer from the redox species in solution to the gold surface. We demonstrate the potential of these hybrid constitutional materials by implementing them as biocathodes and by measuring laccase activity that reduces dioxygen to produce water

Auto-assemblages photo-induits des dérivés triarylamine

Le but de cette thèse était d auto-assembler des entités triarylamines donneurs d électrons et capables de s empiler en fibres conductrices sous l action de la lumière, avec des entités accepteurs d électrons de manière à obtenir des hétérojunctions supramoléculaires. Ces objectifs ont été atteints dans des versions dites statiques (distances constantes entre canauxdonneur et accepteur d électrons) mais aussi dans une version dynamique ou la distance entre unités électroactives change grâce à l action contrôlée d un muscle moléculaire intégré. Ces systèmes auto-assemblés fonctionnels ont montré des changements très importants de leurs propriétés optoélectroniques en réponse à des stimuli orthogonaux comme la lumière et le pH.The aim of this thesis was to self-assemble electron-donating triarylamine units, capable of aggregation into conducting fibers triggered by light, with electron-accepting entities to obtain supramolecular heterojunctions. These objectives were attained, that is in static versions (with constant distances between electron-donating and -accepting channels) and in a dynamicversion wherein the distance between the electroactive units changes owing to the controlled action of an integrated molecular muscle. These functional self-assembled systems showed very important changes in their optoelectronic properties in response to orthogonal stimuli such as light and pH.STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF

Formation hiérarchique de gradients (bio)fonctionnels fondés sur des monocouches auto-assemblées stimulables par le pH

Nous avons démontré au cours de ce travail la possibilité d étendre la chimie combinatoire dynamique aux surfaces et de réaliser des interfaces capables de se réorganiser dans l espace et dans le temps. Afin de démontrer une preuve de principe et d illustrer le potentiel de la technique nous avons développé des DynaSAMs permettant la construction hiérarchique des gradients mixtes composés par des molécules fonctionnelles ou par des protéines. Cette thèse est composée de deux parties principales. La première concerne la conception, la synthèse et la caractérisation des molécules cibles. La deuxième décrit la fonctionnalisation des surfaces avec ces molécules aussi bien que leur dynamique d échange dans l espace et dans le temps. L aspect synthétique consiste à fonctionnaliser des fluorophores de type cyanines par des amines ayant différents pKa comme groupes de reconnaissance. Ces molécules ont été ensuite greffées sur une surface recouverte d une monocouche d aldéhyde via des liaisons imines réversibles. La possibilité d obtenir plusieurs types de gradients fluorescents par modulation du pH nous a permis d établir une preuve de principe de cette nouvelle approche. La généralité de cette technique a été illustrée par l élaboration des gradients de mouillabilité à partir d un mélange d amines portant des entités hydrophobes et hydrophiles et surtout par la formation des biomatériaux qui sont composés par des gradients de protéines de type avidine et streptavidine. L approche DynaSAMs ouvre une nouvelle approche vers la conception des systèmes interfaciales stimulables qui peuvent adapter leurs constitutions à des paramètres externes.In this work we show that dynamic covalent chemistry can be used to functionalize surfaces in such a way that their interfacial properties can be controllably varied in space and time. As a proof of principle and in order to illustrate the potential of this technique we have developed DynaSAMs which enable the hierarchical construction of mixed gradients that are comprised of either small functional molecules or proteins. This thesis is divided into two main parts. The first one concerns the design, synthesis and characterization of our target molecules. The second one described surface s functionalization with these molecules as well as their dynamic exchange in space and time. The synthetic aspect consists in functionalizing cyanines type dyes by different amines as recognition groups having different pKa. These molecules can then be grafted onto an aldehyde functionalized surface using reversible imines bonds. The possibility to obtain many types of fluorescent gradients by pH modulation allowed us to establish a proof of principle for the new approach. The generality of this technique was illustrated by the elaboration of wettability gradients from a mixture of amines bearing hydrophobic and hydrophilic entities and especially, by the formation of biomaterials which are composed of avidine and streptavidine proteins gradients. The DynaSAMs approach opens up an interesting research framework related to the design of new responsive interfacial systems that can adapt their constituents to external parameters.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Triarylamine-Based Supramolecular Polymers: Structures, Dynamics, and Functions

International audienceTriarylamine molecules and triarylamine-based covalent polymers have been extensively investigated for more than 60 years in academics and industry because of their intriguing electronic and optical characteristics. However, despite the profusion of studies made on these derivatives, only very recently have the first examples of supramolecular polymers based on the triarylamine motif been described in the literature. Specifically, our research group has shown that, by adding supplementary hydrogen bonding moieties such as amide functions in their periphery, it becomes possible to tightly pack triarylamine molecules in columnar supramolecular stacks presenting a collinear arrangement of their central nitrogen atoms. These supramolecular polymers can self-assemble into various soft hierarchical structures such as helical fibers, nanorods, nanospheres, and nanoribbons in the sol and in the gel states, into liquid-crystalline mesophases, and into highly organized supramolecular frameworks and single crystals thereof.Interestingly, the associated supramolecular polymerization mechanism involves a nucleation step of high activation energy, which requires the flattening of the triarylamine core. Because of this singularity and although dependent on the precise chemical nature of the building blocks, it has been demonstrated that their supramolecular polymerization can be triggered by original tools, such as light irradiation or electrochemistry, and that it can display autocatalytic growth behaviors, remarkably strong amplifications of chirality, and complex and competing thermodynamic and kinetic self-assembly pathways.Further, from a functional point of view, it has been highlighted that a partial oxidation of the triarylamine molecules results in an enhanced through-space delocalization of the charge carriers along the π–π stacked supramolecular polymers, a feature that confers to these nanowires exceptional transport properties. Upon increasing the charge carrier concentration, the electronic nature of these soft materials can be switched from semiconducting to metallic behavior, and the presence of highly delocalized unpaired electrons in supramolecular polaronic band structures has been further exploited to implement plasmonic properties within subwavelength organic interconnects and microscopic optical waveguides.Finally, by making use of the unusual dynamics and functions of triarylamine-based nanostructures, it becomes possible to precisely address their self-construction within confined environments or within nano- and micrometer scale devices. This has been demonstrated for instance between nanoparticles and between electrodes, inside inorganic nanopores, and inside phospholipid bilayers, as well as at the liquid–liquid interface. Such a meeting point between bottom-up and top-down technologies is of high interest to envision further developments and applications for this entirely new class of supramolecular polymers, which combine a unique relationship between their structures, their dynamics, and their subsequent emerging functional properties

Catalytic accordions

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Extraction of mechanical work from stimuli-responsive molecular systems and materials

International audienceMolecular switches and advanced molecular motors, which are the elementary building blocks for the construction of molecular machines, have been recently integrated into soft materials in order to generate macroscopic actuation under various types of external stimulations. However, to produce a continuous work from these materials, and therefore to potentially achieve more advanced tasks, important structural and dynamic aspects should be considered at all length scales. Here we discuss the implementation of thermodynamic, photodynamic, and dissipative molecular switches and motors in such stimuli-responsive materials. We also highlight the different ratcheting strategies that can be implemented in these actuators to confer them with the capacity of achieving unidirectional cyclic motion, and in order to continuously and autonomously increase their work output

Light-Driven Molecular Whirligig

International audienceAn unidirectional light-driven rotary motor was looped in a figure-of-eight molecule by linking two polymer chains between its stator and rotor parts. By properly tuning the size of these linkers, clockwise rotation of the motor under UV light was shown to create conformationally strained twists between the polymer chains and, in this tensed conformation, the energy stored in the molecular object was sufficient to trigger the reverse rotation of the motor back to its fully relaxed state. The functioning principle of this motorized molecular device appears very similar to the one of macroscopic whirligig crafts used by children for fun. In addition, we found that in its out-of-equilibrium tensed state, the fluorescence emission of the molecular motor increased by 500% due to the mechanical constraints imposed by the polymer chains on its conjugated core. Finally, by calculating the apparent thermal energies of activation for the backward rotations at different levels of twisting, we quantitatively determined a lower estimate of the work generated by this rotary motor, from which a torque and a force were extracted, thus answering a long-term open question in this field of research